In the earliest days of the most recent Zika virus pandemic, researchers around the world set out to understand every facet of a contagion that seemed almost uncontrollable. While some researchers and physicians studied the pathophysiology of the virus and the seemingly minor illness it caused, ecologists and entomologists sought out the virus’s origin and vector. When it was discovered that Zika virus was detrimental to fetal development even when the baby’s mother showed no outwards signs of infection, microbiologists and engineers at the University of Pennsylvania began designing a diagnostic tool that detected the virus in bodily fluids.
Recently, Dr. Jinzhao Song and his colleagues at the University of Pennsylvania published a paper in the journal Analytical Chemistry that described how their small, portable device detected Zika virus in less than 40 minutes. The device, which scientists call a microfluidic cassette, works by specifically detecting the Zika virus’s genome. This is accomplished through the use of primers which are small segments of genome that are attracted to other genome segments of homologous structure. Primers can be thought of like magnets for DNA and RNA. Scientists ensured that the primers in the cassette would specifically recognize the Zika virus’s genome by modeling them after the genetic sequences of the most common Zika virus strains from Mexico, Suriname, and Columbia.
If the primers detect a part of the Zika virus’s genome, they bind to it, and the nucleic acids (which make up the genome) are then concentrated and purified on the cassette. The enzymatic activity involved in concentrating and purifying the Zika virus genome causes a normally colorless dye to change color and become purple.
This process of detecting and amplifying a virus’s genome is called “reverse transcription-loop mediated isothermal amplification” or “RT-LAMP” for short.
Importantly, the cassette fits in the palm of one’s hand, and moreover, it does not require electricity. Instead, this detection and amplification reaction takes place in an insulated cup where a second reaction produces energy that can be transferred to the cassette.
The device can easily be transported to remote or rural areas, and it is also inexpensive to make – it costs about $2 per device. “Our system is particularly suitable for resource-poor settings, where centralized laboratory facilities, funds, and trained personnel are in short supply, and for use in doctor’s offices, clinics, and at home,” Dr. Song and his associates wrote.
Source: Analytical Chemistry
Although there already existed many ways to detect viruses and bacteria in the human body, most of these tests were not viable options for Zika virus because they weren’t sensitive enough to detect the low levels of viral RNA or proteins. This new cassette is sensitive enough to detect Zika virus in blood, saliva, urine, and semen.
“Rapid and reliable diagnostics for [Zika virus] are vital because [Zika]-infected individuals display no symptoms or nonspecific nonsyptoms similar to other viral infections,” the authors wrote. “This convenient, inexpensive, portable assay strategy has the potential to meet urgent needs in endemic regions with stressed resources,” they added.
Picture Credit: http://www.freeimages.com/photo/mosquito-1-1372781
- Song, J., Mauk, M., Hackett, B., Cherry, S., Bau, H., and Liu, C. Instrument-Free Point-of-Care Molecular Detection of Zika Virus. June 2016. Analytical Chemistry.
- Zika virus strain Mr 766. Viralzone.org.
- Zika virus key facts. World Health Organization.